As winter put the freeze on in the southern hemisphere of the Red Planet, the Mars Exploration Rovers slowed down a bit, but continued throughout February to demonstrate the mettle that made them famous: Spirit successfully drove backwards, parked in place for the season, then continued working, as Opportunity roved through rock debris on a cruise around the rim of Concepcin Crater.

It was January of 2004 when the elegant curve of the Vichada first caught the attention of geologist Max Rocca of Buenos Aires. Could the course of the river have been shaped by the circular outlines of an impact crater? Rocca decided to find out.